Derivate des Borols, XVIII. Tricarbonyl[η5‐(1‐phenylborol)]eisen: Zur Reaktivität der koordinierten Liganden

Derivatives of Borole, XVIII. – Tricarbonyl[η5‐(1‐phenylborole)]iron: Reactivity of the Coordinated Ligands The borole complex (C4H4BPh)Fe(CO)3 (1) undergoes Friedel‐Crafts acetylation (MeCOCl/AlCl3) at the meta‐position of the phenyl substituent while the derivatives (C4H4BPh)Fe(CO)2L (3, a: L = NMe3′ b: L = PMe3) are acetylated at the 2‐position of the borole ring. Organolithium reagents (LiMe, LiBu) add to 1 at the boron atom below – 50°C while nucleophilic attack at the carbonyl C atom takes place at higher temperature with formation of acyl anions [(C4H4BPh)Fe(CO)2(COR)]− (6a,b−). The Fischer carbene complex (C4H4BPh)Fe(CO)2[C(OMe)Me] (7) is obtained from 6a−/[Me3O]BF4. Complex 1 reacts with LiN(SiMe3)2 to give [(C4H4BPh)Fe(CO)2(CN)]− (8−) and with 5 M NaOH/C6H6/NBu4HSO4 to produce the hydride NBu4‐[(C4H4BPh)FeH(CO)2] (NBu4 · 9). A highly reactive dianion [(C4H4BPh)Fe(CO)2]2− (102−) is obtained by deprotonation of 9− or by reduction of 1 or 3a in THF at −70°C. Treatment of 102− with Ph3SnCl gives [(C4H4BPh)Fe(CO)2(SnPh3)]− (11−) which is isolated as NEt4 · 11. Slow reduction of 3a with sodium amalgam in THF at −30°C produces doubly CO‐bridged cis‐[{(C4H4BPh)Fe(CO)2}2]2− (122−) which is protonated to the μ2‐hydrido anion [μ‐H‐{(C4H4BPh)Fe(CO)2}2]− (13−).